Fiorentina, welcome to the forums!
If the two large plants were immersed in water, that's what caused them to drop all of their flowers suddenly. Their roots have more than likely started to rot. If you're near a store with a garden center, you might pick up a bag or two of orchid bark and repot those guys after cutting away any dead and mush roots. We've got a repotting guide on the site here. Go to the middle of the page, click the link "How do you repot an orchid?"
A lower leaf turning yellow is usually normal on Phals, so if you've caught the root rot early enough, that shouldn't be a cause for concern. If the yellowing leaf is not one of the two lower ones, that could mean problems, and you should repot the plants as soon as you can.
The littlest one sounds like it's doing fine--though you should probably start fertilizing all of them.
That link to our care section above is geared toward begining orchid growers, so that's a good place to start collecting "how to" information, and be sure to use the forum's search function for keywords like "root rot," "repotting," etc. since there's a lot of info that's been posted about that stuff.